1. Field of the Invention
The present invention relates to a burning or combustion apparatus having a built-in storage battery, and more particularly, to a combustion apparatus which utilizes combustion heat generated by the combustion apparatus to charge the storage battery so as to operate electric loads such as an ignitor or the like using the electrical energy stored in the storage battery.
2. Description of the Related Art
Conventionally, in combustion apparatuses adapted to drive associated electric loads by the use of combustion heat generated thereby, there is known a type which comprises not only a thermoelectric generator element serving as a power supply but also a storage battery for storing electrical energy generated by the thermoelectric generator element.
An example of a combustion apparatus having a built-in storage battery is shown in FIGS. 3A and 3B.
The illustrated combustion apparatus, which may be a thermal cooking range, is provided with a thermoelectric generator element 4 for generating a thermal electromotive force, a booster circuit 8 for boosting a voltage generated by the thermoelectric generator element 4, and a storage battery 12 for storing the boosted voltage.
When burning or combustion is started, electrical energy stored in the storage battery 12 is used to operate an ignitor 14 which discharges the supplied electrical energy to ignite a combustible gas. Also, electrical energy is thermally generated by the thermoelectric generator element and stored in the storage battery 12, such that the stored electrical energy can be utilized as driving power for the ignitor 14.
If, however, stored electrical energy in the storage battery is depleted, the storage battery cannot be internally recharged by the thermoelectric generator element 4 and the booster circuit 8 unless the storage battery itself is replaced or the storage battery is externally recharged by another method. This problem will be more specifically discussed below.
Originally, the thermal electromotive force generated by the thermoelectric generator element 4 is too low to directly charge the storage battery 12. The booster circuit 8 is therefore provided for boosting the voltage generated by the thermoelectric generator element 4, whereby the storage battery 12 can be charged by applying the boosted voltage thereto.
However, since the booster circuit 8 is operated with electrical energy stored in the storage battery 12, if an amount of the electrical energy stored in the storage battery 12 is lowered to such a degree that the booster circuit 8 cannot be operated therewith, the storage battery 12 can no longer be recharged by the thermoelectric generator element 4 and the booster circuit 8.
Assuming, for example, that a nickel-cadmium storage battery is used as the built-in storage battery, a minimally required voltage for charging is 1.2 volts. Also, a voltage ranging from 0.6 to 2.0 volts or more is required to drive loads of the apparatus including ignitor 14, other operation lamps, etc. On the other hand, the thermoelectric generator element 4 has a capability of generating a thermal electromotive force of approximately 0.4 volts.
Therefore, the thermal electromotive force generated by the thermoelectric generator element 4 cannot be utilized as it is for charging the storage battery 12, and the booster circuit 8 is therefore required to boost the thermal electromotive force.
Thus, if the voltage stored in the storage battery 12 is lowered to such a degree that the booster circuit 8 cannot be operated with the stored voltage, the storage battery 12 cannot be charged using the thermal electromotive force generated by the thermoelectric generator element 4.
For the reason mentioned above, if an amount of electrical energy stored in the storage battery 12 has been lowered below a required level due to natural discharge which occurs during a period of non-use of the combustion apparatus, the user must take countermeasures, such as external recharging or exchange of the storage battery 12. These countermeasures can be expensive, troublesome, and time-consuming.
Alternatively, a backup power supply must be provided for the storage battery 12, previously supposing a decrease in the stored amount of electrical energy in the storage battery 12. This, however, would end up having the same problems and requiring the same countermeasures as with the system discussed above, if the backup power supply is exhausted.